I have a vague recollection that there is or used to be a guide to the Dales Way which did the whole thing as a series of circular walks, some of those might be good, as they wouldn't be too hilly.
Or something like get the train to Burley, walk over the moors to Ilkley and get the train back. The train might offer added interest.
My eldest's first hill was Simons Seat, we went up by the Valley of Desolation and came down the shorter way, but I do remember it was a bit too far, but you don't have to do it as a round.
There a few nice short rounds in the Washburn Valley, eg round Swinsty reservoir.